The prognostic value of the tumour-stroma ratio in primary operable invasive cancer of the breast: a validation study.

Purpose: The primary aim of the current study is to validate the prognostic relevance of the relative amount of tumour-associated stroma, the tumour-stroma ratio, in a large cohort of primary operable breast cancer patients.
Methods: A retrospective cohort study was performed on women diagnosed and treated for primarily operable invasive breast cancer in the period from 1 January 1990 till 31 December 1999. Tumour-stroma ratio was estimated by microscopic evaluation of haematoxylin and eosin tumour slides. Two independent observers (k = 0.68) performed tumour-stroma ratio evaluation in a significant part of the cohort. The prognostic potential with respect to overall, recurrence-free and distant metastasis-free survival was evaluated.
Results: A total of n = 737 women were evaluated. Median follow-up time was 11.5 years. High stromal content was an independent prognosticator for worse overall (hazard ratio 1.56, p = 0.002, 95% confidence interval 1.18-2.05), distant metastasis-free (hazard ratio 1.52, p = 0.008, 95% confidence interval 1.12-2.06) and recurrence-free survival (hazard ratio 1.35, p = 0.046, 95% confidence interval 1.01-1.81). In subgroups of hormone receptor-positive and lymph node-negative cases, high stromal content was also an independent prognosticator for worse outcome.
Conclusion: Tumour-stroma ratio is an independent risk factor for worse overall, distant metastasis-free and recurrence-free survival in primarily operable breast cancer. However, detailed prospective studies with respect to tumour-stroma ratio are necessary to gain more insight in its prognostic potential in clinical practice.